Telephone switchboard apparatus and circuits therefor.



H. J. ROBERTS. TELEPHONE SWITGHBOAED APPARATUS AND CIRCUITS THEREFOR.

A'PPLIGATION FILED 00113, 1906. RENEWED NOV. 21, 1911.

1,031,667, Patented July 2, 1912.

2 SHEETS-SHEET l.

H. J. ROBERTS. TELEPHONE SWITGHBOARD APPARATUS AND CIRCUITS THEREFOR.

APPLICATION FILED OCT. 13, 1906. RENEWED NOV. 21I 1911.

1,031,667. Patented July 2, 1912.

2 SHEETSSHEET 2.

COLUMBIA PLANOGRAIH cu wAsmNo'ron, I): :4

Original application filed September 5, 1905, Serial No. 276,975.

October 13, 1906, Serial No. 338,384. Renewed November 21, 1911.

UNITED STATES PATENT OEFIQE.

HOMER J. ROBERTS, EVANSTONi ILLINOIS, ASSIGNOR, BY MESNE ASSIGNMENTS, TOHOMER ROBERTS TELEPHONE CO., A CORPORATION OF WEST VIRGINIA.

TELEPHONE SWITCI-IBOARD APPARATUS AND CIRCUITS THEREFOR.

To all whom it may concern:

Be it known that I, HOMER J. ROBERTS, a citizen of the United States,residing at Evanston, in the county of Cook and State of Illinois, haveinvented certain new and useful Improvements in Telephone SwitchboardApparatus and Circuits Therefor, of which the following is aspecification.

This invention relates to telephone switchboard apparatus and circuitstherefor, and it has for its general object the provision of selectivecalling apparatus and circuits therefor by means of which all of thecord controlling keys pertaining to a particular group or section areplaced under the direct control of a master-key which in turn controlsthe selective calling apparatus and also effects the conversion orspecialization of cords or cord pairs for the time being so that theymay be used for making connections with selective party-lines.

Further objects of the invention are to provide a system which issusceptible of being installed in ordinary manual exchange switchboardswithout to a serious extent necessitating the re-wiring or disturbing ofthe switchboard connections already installed; to provide a systemadapted to act or combine with a special form of automatic counting outmechanism, which latter forms the subject of another application; toprovide a system of the character referred to which is so organized asto admit of com bining therewith both a calling-in signaling system anda supervisory signaling system; and in general to provide an improvedsystem of the character referred to.

To the above ends the invention consists in the matters hereinafterdescribed and more particularly pointed out in the appended claims.

The invention will be readily understood from the following description,reference being had to the accompanying drawings forming a part thereof,in which Figures 1 and 1 taken together represent diagrammatically thecomplete switchboardv circuits and operating mechanism.

In the particular embodiment of the invention illustrated, it isdesigned for use in a switchboard which has both selective party-linesubscribers and individual line subscribers; the selective party-linesbeing Specification of Letters Patent.

Patented J uly'2, 19121 Divided and this application filed Serial No.661,633.

of that type in which the selections are per formed by counting out adefinite number of impulses of current of one polarity and the ringingof the several parties effected by throwing onto the line pulsatingcurrent of a polarity opposite that employed in se lecting. In thepresent system two sets of signaling apparatus are embodied, onecontrolling the line drops and operated by common battery, the othercontrolling self-restoring supervisory signals and also operated bycommon battery. The supervisory signals are individual to the severalpairs of cords so that each signal is in use only as its correspondingcord is in use.

In practice, in adding to an ordinary manual exchange switchboardalready installed selective party-lines, the cord keys already installedmay be and usually are utilized by simply adding additional pairs ofcontact strips and additional bus-lines connecting each of the cord keysso converted to the master-key set. Thus ar ranged, the operatordesiring to use any given pair of cords for connecting between twoparty-lines, or between one party-line and an individual line, simplyplaces the key controlling that pair of cords in its selfretainingposition and thereafter performs the further work of completing theconnections through the master-key, as well as the operation (which isusually necessary in lock-out party-line systems) of clearing, i. e.restoring the line to normal.

Referring now to the diagram, A, A, A designate a plurality of cordkeys, and B, B, two somewhat similar keys which latter togetherconstitute the complete master-key set.

C designates diagrammatically a source of usual alternating callmgcurrent, the generator shown being connected by bus-lines 1 and 2 withthe several cord keys.

I) designates as a whole diagrammatically a generator so arranged as toafford pulsations of either polarity.

E designates as a whole an automatic pulsation-counter, which forconvenience of description will be herein termed a selector; itsfunction being to count out a definite number of pulsations and in thismanner effect selection of the particular party wanted on a party-line.

F designates a main battery, which affords current for various purposes,and G a second battery of a less number of elements which suppliescurrent for both signaling systems.

H, H, H designate a plurality of springjacks forming the terminals ofcorresponding metallic lines, and I, I, I corresponding line drops. Eachcord key is provided on each side wit-h inner pairs of contacts, as 3,3, 4, 4L and 5, 5 and 6, 6, which, in the intermediate position of thekey, are closed. The springs 3, 4, 5 and 6 are respectively connectedwith the tip and sleeve sides of the cords, as 7 8, 9 and 10, and areshifted into contact with outer springs 11, 12, 13 and 141,respectively, when the key is shifted in one direction or the other. Ofthese latter springs, 11 and 12 are connected with the bus-lines 1 and2, respectively, while thesprings 13 and 14. are connected with anotherpair of bus-lines 15 and 16, respectively. These latter lines lead tothe master-key and, as will be seen by tracing the circuit, connect themaster-key with the answering cord sides of the several keys A, A, A Theadditional springs which are added to each key are indicated at 17, 18and 19, 20, respectively; the moving members 18 and 19 being connectedwith but insulated from the corresponding springs 13 and 1 1. Springs 18and 19 are respectively connected with the left and right sidesofanother pair of bus-lines 21, 22, while the cooperating springs 17 and20 are respectively connected with the innermost springs 3, 4 of theopposite side of the key and also with the innermost springs 5, 6 of thesame side of the key. A condenser 23 is interposed in the connectionleading from spring 17 to spring 5, 2'. e. from the tip side,

to prevent interference with the proper operation of the supervisorysignal when a Roberts line is connected .to an ordinary bridged line.The connections of each key A, A, A are precisely similar.

Referring to the master-key set, the key B is so organized that whenshifted in one direction (downwardly, as shown) it throws currentthrough the selector E and to the answering cord of whatever cord key isin use and shifted to a self-retaining position. Similarly when key B isshifted in the opposite direction it throws current through the selectorE to the connecting cord of the same cord key. In either of the shiftedpositions of key B the current sent to line may be pulsating positive orpulsating nega tive, depending upon the position of the selector E. Thatis to say, the selector E when rotating sends current of one polarity toline but as it reaches its normal or zero position it reverses theconnections and sends current of opposite polarity to line. i It will beseen from the foregoing that key B is utilized for calling thesubscribers. Connected with key B so as to move positively in bothdirections with the latter is a subsidiary key B which is so constructedas to shift the springs controlled thereby whenever it moves in eitherdirection. This key performs various functions as will hereinafterappear, chief among which being the control of the battery connections.Key B is so organized as to place the main battery E which is ofrelatively large capacity directly to the left-hand side of the line andat the same time to ground at the opposite side of the battery; theshifting of the key in one direction (downwardly, as shown) serving tothrow the main battery direct to the answering cord and the shifting ofthe key in the opposite direction sending the current to the connectingcord. Connected with key B is a subsidiary key B similar to thesubsidiary key B but so connected that it moves with key B in onedirection only, namely when the latter key is shifted upwardly. Themechanical connection whereby'this is effected is indicated at 24wherein the stem of key B telescopes within a sleeve connected with keyB; the end of the stem of key B terminating in proximity to the body ofkey B. Key B is provided with a stem and push button whereby it may bedepressed and when so depressed it obviously forces with it key B.

The functions of key B are in general similar to those of key B. Anauxiliary push button J is provided which is mounted on one side of alever pivoted at 25, the opposite end of the lever being operativelyconnected with the stem of key member B The push button J controls agroup of conparticular party-line system for which the present inventionis in this instance specifically adapted, any subscriber who calls in islocated and connection given him by looking out all stations between hisset and central, and this looking out is effected by operating therelays at the several stations one after another'by a series ofpulsations thrown to line through push button J. Since this operation isin effect running down the line until the station is reached from whichthe subscriber has called, the push button J will be designated therunning key. A call for connection coming in over a subscribersparty-line would throw the line drop, as for example at I, whereupon theoperator would insert a plug of any available answering cord and securetalking connections and take the order from the calling subscriber asfollows: Observing that the call was on a party-line she would shift thecord key to its self-retaining position, thus extending the circuitsfrom the g. a

spring jack over conductors 9, 5 and 13 to bus-line 15 and overconductors 10, 6 and 14 to bus-line 16, thereby extending theconnections to the master-key set. Buslines 15 and 16 are connected withthe master-key set through conductors 26 and 27 and the circuit closedby the running key in responding to the subscribers call may be tracedas follows: over line 26 to intermediate spring 28 of key B, innerspring 29, conductor 30 to intermediate spring 31 of running key, toback spring 32, thence over conductor 33 to conductor 34, from the.

latter over conductor 35 to the pole changer, from the pole changer overconductor 36 to front spring 37 of the selector, thence to theintermediate spring 38, from the latter over conductor 39 to a contactarm 40, thence over conductor 41 to conductor 34 which connects byconductor 42 with the back contact 32 of the running key, which is atthis time closed with intermediate spring 31. The latter, ashereinbefore described, is connected with conductor 27. This completesthe circuit.

The result of throwing pulsations of one polarity over the circuitdescribed is to lock out the subscribers successively until thesubscriber is reached who called for the connection. By operating hisswitch hook or some other suitable act the subscriber places his set insuch condition that succ'eeding impulses, after his instrument has beenreached, will fail to pass the same. But although he thus arrests thefurther selection it is necessary to put one or more impulses ofopposite polarity through his set in order to place the same in talkingcircuit. This reverse polarity impulse is sent over the line by shiftingkey B clownwardly, which results in transposing the connections betweenthe generator D and the line. This reverse is not made until an amplenumber of impulses have been sent out to more than reach thesub-station; the excess impulses being ineffectual. That part of thecircuit which is reversed may be traced from the generator over theconductor 35 to line 34, thence to outer spring 43 of key B, thence toswitch spring 44, over conductor 45 to inner spring 46 of the runningkey, to switch spring 31, thence over line 27 to bus-line 16, which isconnected through the cord key to the sleeve side of the line. From theother side of the generator the circuit is over conductor 36, springs 37and 38, conductor 39, arm 40, conductor 41 to spring 43 of key B, thenceto switch spring 44 and thence to inner spring 46 of the running keyover conductor 45. From spring 46 the circuit is through spring 31,thence over conductor 30 to and through springs 29 and 28 of key B andto bus-line 15 over conductor 26.

In the self-retaining position of the cord keys the exchange operatorsset is in listening connection with both ends of the cord. The listeningconnections with the answering end of the cord may be traced from buslines 15 and 16 as follows: over conductor 26, springs 28, 29, conductor30, springs 31 and 46 of the running key, conductor 45, springs 44 andan inner spring 48 of key B, through a condenser 49, thence over aconductor 50 to the tip side of operators jack 51. The other side isover conduct-or 27, springs 31 and 46 of the running key, conductor 45to switch spring 44 and inner spring 48, thence through condenser 49 andover conductor 50 to spring 52 of key 13", to spring 53 and back overconductor 54 to the sleeve side of the operators jack.

The listening circuit connections with the calling end of the cord arefrom bus-line 21 over a conductor 55, to switch spring 56 of key B, toinner spring 57, thence over conductor 58 to switch spring 59 of key B,thence to inner spring 60, and thence over conductor 61 to conductor 50and to the tip side of the jack. Similarly from bus-line 22 overconductor 62 to switch spring 59, inner spring conductor 50 and thenceto the sleeve side of the jack as before traced. The operator, havinganswered the subscriber, takes his order for a connection. It a party onan individual line were wanted the connection would be made by simplyinserting the connecting or calling end of the cord in the proper jackand shifting the cord key into its reversed position, thereby throwingringing circut from the bus-lines 1 and 2 through the called subscribersbell. If, however, a party-line connection is called for, the nextoperation will be to insert the connecting end of the cord in the properjack and select and call the particular party wanted. The firstoperation, after inserting the plug, will be to set the selector dial tothrow upon the line as many impulses (which are automatically countedout by the selector instrument) as will effect the selection of theright party. The selector E is so constructed that the dial andconnected ratchet are spring-returned to the Zero position, and thereturning movement is con trolled by a magnet K the armature 7c of whichconstitutes an escapement lever. By means of a suitable handle the dialis manually turned forwardly as many notches as will correspond with thenumber of the party wanted counting the sub-stations outwardly fromcentral. The magnet escapement permits the dial to return one notch foreach impulse, and as the dial reaches the Zero position it is arrestedby a stop-pin 63 engaging a suitable stationary stop 64. Cams 65 and 66are mounted upon the ends of the respective switch springs 38 and 38 ofthe selector, and these cams in the Zero position of the dial rest inrecesses 67,

67, respectively formed in an insulated hub 68 carried on the shaft ofthe selector and rotating with the ratchet of the latter. As soon as thedial is moved away from the zero position these cams are forced out 'ofthe V shaped recesses and thereafter ride upon the periphery of the hub,thus moving the switch springs 38 and 38 outwardly into bearing withback contact springs 69 and 70, respectively. The shifting of the switchsprings in this manner reverses the connections with the pole changer D,so that while selecting impulses are sent to line during the return ofthe selector to zero, when' the selector reaches zero impulses ofopposite polarity or ringing current is sent to line. Pressing the key Bupwardly shifts its switch springs 59 and 59 outwardly into contact withouter springs 71 and 71, and these springs are connected with conductors34 and 34, respectively, so that impulses are sent to line insubstantially the same manner as when operating the running key.

A local circuit is closed through and operates the magnet K when the keyB is closed in either direction, (provided the selector has been set)which current may be traced as follows: from the generator throughconductor 36 and spring 38 to back contact 70, thence over a conductor72 to and through the magnet K, thence to a switch spring 73 pertainingto key B, from the latter to cooperating spring 74, which spring isconnected with conductors 34 and 35, which lead back to the oppositeside of the pole changer.

In the present invention a system of supervisory signals is providedwhich notifies the exchange operator whenever either party has ceasedtalking and hung up his receiver, thus indicating that the lineshould becleared. The subscribers set is so organized that hanging up thereceiver closes a full metallic bridge at his station; itbeingunderstood that the talking circuit at the subscribers station isthrough a condenser so that battery cannot flow. Describing thissupervisory system, 75 designates a bus-line, and between this bus-lineand the answering end of each cord is interposed a self-restoring signal76; the conductors 77 in which these signals are interposed beingconnected with the sleeve side of the respective answering ends of thecords. Line 75 extends to and is connected with switch spring 78 of key13. This spring normally engages inner spring 79 which is connected byconductor 80 with the innermost spring 81 of key B. This is normallyclosed wit-h an opposed spring 82 which is connected by conductor 83with signal battery G. The opposite side of the battery is connected toa conductor 84 which forms a bus-line com mon to all of the line dropsI, I, I, etc.,

line 84 and the tip springs of the corresponding jacks. It follows thatwhenever the subscriber connected with the answering end of the cordhangs up his receiver, the self-restoring signal 76, pertaining to thecord in use, is energized and indicates the line should be clear. Atthis point it may be explained that the line drops are operated by thebattery G at central and that said operation is effected by groundingthe line at the subscribers station. Ordinarily a flash-ground effectedduring the upward movement of the switch hook is employed to throw theline drop. The connection from line 84 through the battery G to groundis over conductor 83, spring 82, switch spring 73, a conductor 85 to aninner spring 86 cont-rolled by key B", from the latter to switch spring78, thence by conductor 87 to a conductor 88 which connects the twoswitch springs 56 and 28 of key B with each other and to ground at 89over a conductor 90. Inasmuch as those subscribers between central andthe party selected are locked out in the act of selecting the latter, itfollows that means must be provided for clearing or restoring thelook-out instruments to normal. As much of the subscribers circuit as isnecessary to understand this operation is shown at L and M at the footof Fig. 1; the party-line being shown connected with the spring jack H.

The clearing of the lines is effected by closing a ground-to-groundcircuit from central at one end through the main battery at central,over the left or tip side of the subscribers line through the severalclearing relays which-are in series with said left line and to ground atthe last subscribers set. At the remote end of the left-hand line islocated a circuit-catching instrument N comprising acondenser,100,amagnet 101 in series with the condenser and connected toground at 102, and a shunt conduct-or 103 which leads around thecondenser to an armature 104 which, when in closed position, engages acontact 105 connected with a few of the coils of the main magnet in suchmanner as to form a self-retaining circuit.

It is necessary to clear both the calling and called subscribers if bothare partylines, and the key B is so constituted as to effect clearing ofthe answering end of the cord when shifted downwardly, and theconnecting or calling end when shifted in the reverse direction.Assuming the calling subscribers line is to be cleared, the circuit willbe from ground at.89 to switch spring 28, back spring 91, conductors 92and 93 to battery F, thence by conductors 94 and 95 to back spring 91and switch spring 28, which latter is connected by conductor 26 with thebus-line 15. Line 15 is connected with the tip side of the answering endof the cord through springs 13, 5, and conductor 9. In case the calledsubscribers line is to be cleared, the circuit will be from ground atcentral through the battery over conductors 90 and 88, to switch spring56, thence to back spring 96, to conductors 92 and 93 to battery, frombattery over convductor 94 to 95, and to back spring 96,

thence to switch spring 56 and from the latter to bus-line 21 overconductor 55. Bus-line 21 is connected with spring 18 and engages spring17 which is connected by a conductor 3 with the inner spring 8 of thecord key. Spring 3 is at this time closed with spring 3 which isconnected by conductor 7 with the tip side of the plug.

In the operation of the master-key set, it is necessary that ground hecut off at central when ringing impulses are sent to line; it isnecessary that the supervisory signal and line drop circuit-s beprotected against the main battery and generator D when clearing andringing and it is desirable that the exchange operators set be eithershort circuited or opened before either the main battery or pole changercircuits are thrown upon the line, in order to prevent reports in theoperators ear. It is the function of the supervisory keys B and B toeffect these results. In case the running key J is depressed, the groundat 89 is opened between the springs 7 8 and 86 of key 13, and in casethe key B be shifted in either direction those same contact springs cutoff the main battery F from the conductor 85 which is a part of the linedrop circuit. In a similar manner movement of key 13 opens the circuitbetween springs 78 and 79, which form part of the supervisory circuit.For the same reasons and in the same manner springs 73 and 82 open theline drop circuit at key B, and springs 81 and 82 at the same key openthe supervisory circuit. Movement of key B opens the operators listeningcircuit betweenthe springs 52 and 53, while movement of key B effectsthe same result of preventing a report in the operators receiver byshort circuiting the operators jack through the springs 97 and 98 andthe conductors connected therewith.

In the practical operation of telephone systems difliculty isexperienced in many instances on account of residual magnetism remainingin magnets after they have been energized with current of a givenpolarity, such residual magnetism tending to make the armature stick tothe pole pieces unless cushioned away from the latter by stops whichprevent very close approach of the armature of the pole piece. Inasmuchas the working power of a magnet increases proportionately as the squareof'the distance decreases between armature and pole piece it is obviousthat the employment of a stop which prevents the armature fromapproaching closely to the pole piece, greatly impairs the eificiency ofthe magnet. In any system where the magnet is required to do an amountof mechanical work approaching the whole strength of the magnet it isobvious that the handicap of large cushioning stops is serious. I haveinvented an expedient which obviates these objections by effectuallyclearing out the troublesome residual magnetism, thus leaving the magnetsubstantially neutral when deenergized and avoiding any tendency of thearmature to stick. I accomplish this result by so arranging the circuitsand source of current that following each Working or main impulse sentthrough the magnet or magnets there is sent a very weak impulse throughthe magnet or magnets opposite polarity, which while so weak as to fallfar below the current necessary to operate the magnet or magnets, isnevertheless effectual in neutralizing the residual magnetism. In thepresent instance I effect this result by placing a bridge conductor 106across the two limbs of the circuit which are connected with therepective poles of the generator D and in this conductor interpose aresistance 107 which is so high as to permit but a very slight leakageacross from the limb which is receiving the main impulse to the oppositelimb. It follows that while the pole changer D is sending each impulsethrough the local circuit including the magnet K there occurs a dividedflow or slight leakage across from line 36, through high resistance 107to the line which connects to the external circuit, and this weakimpulse is of opposite polarity to that of the full or unrestrictedimpulse sent over the external circuit.

I claim as my invention:

1. In a manual telephone switchboard system, the combination with aplurality of subscribers lines and suitable terminals located at saidswitchboard, of a connecting cord circuit, a key arranged to control thecircuits through said cord, an impulsecounting selector connected withsaid cord circuit in a normally open key-controlled circuit andcomprising a magnet-controlled actuating mechanism, a source ofpulsating current connected in circuit with said magnet-controlledactuating mechanism, and means for manually setting said selector tocount out a predetermined number of impulses.

2. In a manual telephone switchboard system, the combination with aplurality of subscribers lines and suitable terminals located at saidswitchboard, of a connecting cord circuit, a key arranged to control thecircuits through said cord, an impulse-counting selector connected withsaid cord circuit in a normally open key-controlled circuit andcomprising a magnet-controlled actuating mechanism, a source ofpulsating current connected in circuitwith said magnet controlledactuating mechanism, means for manually setting said selector to countout a predetermined number of current impulses,

' subscribers lines and suitable terminals 10- cated at saidswitchboard, of a connecting cord circuit, a key arranged to control thecircuits through said cord, an impulsecounting selector connected withsaid cord circuit in a normally open key-controlled circuit andcomprising a magnet-controlled actuating mechanism, a source ofpulsating current connected in circuit with said magnet-controlledactuating mechanism, means for manually setting said selector to countout a predetermined number of current impulses, and contact devicesactuated by said selector and operating to automatically reverse theline circuit connections so as to reverse the impulses sent to lineafter a predetermined number have been counted out.

4. In a manual telephone switchboard system, the combination with aplurality of subscribers lines terminating at said switchboard, of acord circuit adapted for connection with said terminals, a keycontrolling said cord circuit, a source of constantly re-. curringuni-directional pulsating current, a selector having aratchet-controlled stepping mechanism, a magnet controlling said ratchetmechanism, means for manually set ting said selector to perform apredetermined number of steps, suitable circuit connections for sendingcurrent through said ratchet-controlling magnet mechanism, suitablecircuit connections for synchronously sending impulses to line andcontact-s actuated by said selector operating to automatically interruptthe sending to line of impulses of a given polarity upon the completionof the counting out of the number of impulses for which the selector isset.

5. In a manual telephone switchboard system, the combination with aplurality of subscribers lines terminating at said switchboard, of acord circuit adapted for connection with said terminals, a keycontrolling said cord circuit, a source of constantly recurringuni-directional pulsating current, a selector having aratchet-controlled stepping mechanism, a magnet controlling said ratchetmechanism, means for manually setting said selector to perform apredetermined number of steps, suit-able circuit connections for sendingcurrent through said ratchet-controlling magnet mechanism, suitablecircuit connections for synchronously sending impulses to line andcontacts actuated by said selector operating to automatically reversethe circuit connections with said source of pulsating current so as tointerrupt the sending to line of impulses of a given polarity uponcompletion of the counting out of a definite number of im-' pulses andefiect the sending to line of impulses of opposite polarity.

6. In an electric system, the combination of an electric circuit, meansfor sending alternate impulses of opposite polarity over said circuit, amagnet in said circuit, and a shunt connected'with one limb of saidcircuit between the source of energy and magnet and operating to reducethe amount of current of one potential sent through the magnet to afraction of the amount of opposite potential current sent there through.

7 In an electric system, the combination of an electric circuit, amagnet in said circuit, and means for sending alternate impulses ofopposite polarity and difi'erentiated strength over said circuit, theimpulses of one polarity being of a strength sufiicient to actuate themagnet and those of the opposite polarity being less than sufficient tooperate the magnet but acting to neutralize residual magnetism in saidmagnet.

8. In an electric system, the combination of a source of energy, aconstantly shifting commutator connected with one pole of 100 saidsource of electric energy, a pair of brushes with which said commutatoralternately contacts, a magnet, a conductor connected with one of saidbrushes, including the windings of said magnet, and connected 105 at itsopposite end with that pole of said source of energy opposite the polewith which said commutator is connected, a second conductor connectedwith the second brush and with the first conductor so as to 110 form ashunt between said brushes, and a resistance interposed in said shunthigh enough to prevent operation of the magnet under normal workingconditions.

9. In an electric system, the combination of a source of electricenergy, a constantly shifting commutator connected with one pole of saidsource of energy, a pair of brushes with which said commutatoralternately contacts, a plurality of magnets, a conductor connected withone of said brushes, including the windings of the several magnets andconnected at its opposite end with the opposite pole of said source ofenergy, a second conductor connected with the second brush and with thefirst conductor so as to form a shunt between said brushes, a resistanceinterposes in said shunt high enough to prevent operation of V themagnets under normal working condi-' tions, an electrically-controlledimpulsepredetermined number have been counted counter connected 1nclrcuit W1th sald source out.

of energ means for manuall settin said counter 0 0 count out a defini te numl er of HOMER ROBERTS impulses, and means operating automati-\Vitnesses:

cally to arrest the sending to line of Work- ALBERT H. GRAVES,

ing impulses of a definite polarity when the EMILIE RosE.

Copies of this patent may be obtained for five cents each, by addressingthe Commissioner of Patents, Washington, I). G.

